Problem with out board!

[Glenn Basore]

Hi all,

Need some more help / advice on out board motor.

I have a 2005 Mercury 4 stroke, 4 hp out board which has never run too good. I am the second owner of this OB and I can tell you I've spent some money on having it serviced since I've had it.

My biggest problem is getting it to idle at low speeds, just stalls out. I must use the choke to get it to at least run at a low speed around the docks. ( the rpms seem awfully high at what should be a low idle)

I've replaced the plug, set the gap,  fuel filter, fuel pump, drained and flush the tank , the hoses all seem good and everything is dry under the hood, no leaks.

There is no adjustments to be made on the carb, only a linkage adjustment for the throttle which doesn't seem to do much.

The gas I use is 87 octane and I was thinking of trying a higher octane before replacing the carb.

One last thing, this motor has all the California emissions on it :-(

Any ideas?

Glenn

[capt_nemo]

Glenn,

Buy a can of "Sea Foam" (available at Wal Mart and Auto Parts Stores) and follow the instructions for "Tune up of Small Engines".

At the very least, run a high concentration mix in FRESH gas out on the water for more than just a short run. It needs time to "work".

It is great stuff. I use it to "maintain" my YAMAHA 4 stroke 4 HP Outboard, RV Generator, Home Standby Generator, and HONDA VTX 1300 Motorcycle.

And, they ALL run great!

Hope this will do the trick.

capt_nemo

[Bob23]

Hi Glenn:
   I'm no outboard mechanic but I'll offer this nickels worth of free advice: Use fresh premium fuel with a stabilzer such as Sta-bil. I've heard that premium has less ethanol in it. I use this combination in my outboards, generator, chainsaw, air compressor...you get the idea.  I don't know if this will solve your problems but it couldn't hurt.
   I've had fuel in some of these for over a year and while that's not a great idea, I just don't empty the fuel just because it's old. That being said, I use all of the above regularly so the fuel never gets ancient. The outboard, however always has fresh fuel. Btw, mine is not a 4 stroke and I've heard the 4 strokes can be finicky.
Bob23

[nies]

         I had the same four stroke merc. and never could get it to run, I think they are lemons, traded in for the last 2 stroke on earth and have been happy ever since...................nies

[skip1930]

For an outboard engine to run lean at idle and run lean at full speed and remain within the emissions limits placed upon manufactures by the EPA/government several things have been happening in the O/B world.

Mostly developing fuel atomizing multi-port jets having very tiny bores* drilled into it. This technology will breakup and deliver vaporized fuel at it's tinyest possible gathering and add to that the largest amount of air [oxygen] and that leans the mixture out for the most complete and particulate free burn. None of this happens without a adequate air speed through the carburetor. And here is the problem at low speed and at idle. And despite the carburetor manufactures best efforts with drilled idle circuits metered by multi-port jets in cast carburetor bodies, this required air speed doesn't happen. Let more air/fuel in she idles too fast.

Sounds good on paper but in reality the mixture created at a low idle-low rpm run just does not contain enough heat energy to support decent combustion. It's almost too darn lean to burn. Combustion engineers have been dealing with complete and lean burns forever.

The most aggravating hair pulling problem that all manufactures and Mercury has is plugged multi-port jets in carburetors. A definite problem on small inexpensive non computerized and carbureted out board engines. Yet as displacement grows, and costs climb, then computers are used, and fuel pumps to pressurize the feed to pulse fuel injectors has resulted in a better running engine.

So the trend today is do away with the carburetor and that eliminates the naturally aspirated jets and deliver a pressurized stream of fuel through a fuel injector.

I would much rather have a good old two stroke engine that runs blubbery rich at idle and makes beautiful rainbows in the water and goes like stink. Sure it pollutes. The solution to pollution is and has always been dilution. For the eight gallons a season I burn of gas/oil the Earth is not going to stop circling the Sun and the fish are still going to be swimming in the pond.

What can be done with this engine? Well if it was me I'd find an older style carburetor that will not meet the current emissions but run well and bolt it on and still use non ethanol premium fuels [BP is one source].

If you don't want to do this, then the carburetor will have to be constantly torn down and cleaned. Fuel filters only filter to around 100 microns and air filters even less. And there is very little, not even 1/2 inch water column of fuel pressure delivering fuel through the jets.

My friend's son is an engineer at Mercury and he talked about fuel jets at our U.S.P.S. boat seminar. This is where I gleaned this information.

Side bar; * multi-port jets will not flow particulate matter larger then 80+ microns and resistance to flow per port is tremendous, hence 'several small ports'.

There in lies the problem.

"...I don't think it is a case of ethanol percentages but more a case of ignition quality of the fuel..."
Yea Mac, I'd agree, a proper 14.7 lb air to 1 lb vaporized fuel ratio through gelatinous plugged jets effects the quality of the burn.

If anyone would ever take the time to carefully read The Super Tuning And Modifying Holley Carburetors book By Dave Emanuel a understanding of airflow would explain why this engine pictured below has been fitted with a 550 scfm carb and not a 750 scfm [standard cubic foot per minute].

X amount of air through a big hole, air slows down and so does 'suction'. Same air through a small hole, air speeds up and 'suction' increases. Bare in mind that the concept of suction does not really exist. It is instead the weight of air PUSHING itself through a hole. Air weighs 1.087 lb per cubic foot at sea level. A piston goes down in a bore, it doesn't really suck in any air. A void is created and that void fills with 'the weight of air' falling into the void. This is what pulls fuel through a jet also.

Many hours were spent changing carbs first, then jets, to make this engine perfect at all rpm's.

skip.

[MacGyver]

Run blue stabil to help breakdown the deposits and junk.
There is also a fuel enzyme that I still need to get the name of........i keep forgetting......

Also only use top grade fuels in marine engines. I dont think it is a case of ethanol percentages but more a case of ignition quality of the fuel .

It will take a little time to get it worked out. As the chemicals need to work on it all. That is a good at home shop project to do.

Make sure you have that engine cycling water when you run it at home........and if you use muffs make sure to watch em that they stay in place... ive had mine come off before......but of course I was there to catch it since I knew my luck would be it would come off.

Mac

[skip1930]

Right now, today the EPA is discussing writting legislation for small engines. Outboard engines, inboard/outboard, lawn mowers, snow blowers, mopeds, generators, pumps, and what have you.

Necessary to achieve this will be fuel injection and all that goes with that and in addition to 'include exhaust catalytic converters' on small gasoline powered engines...the engine sizes are being batted around. I have read in our U.S.P.S. Boat U.S. magazine articles suggesting sizes as low as 50 cc and an upward start at 150 cc.

I for one want nothing to do with this crud. You do realize that watching the water flow over Niagara Falls for eleven minutes and something seconds is equal to the fuel vaporized and burned every day in America. It is only about 17% of the crude that is pumped out of the ground according to National Geographics, that can be cracked into light hydrocarbon fuels.

skip.

[brackish]

Do these little outboards have T-stats?  I've noticed my 9.9 Suzuki four stroke has the low speed problem seasonally.  The difference in the water temp is about 40 degrees.  I've found that in the winter, no matter how long I've run the motor, I have to keep it partially choked to keep it from stalling out at low speeds, and as a result, It has to run at a slightly higer RPM when trying to idle.  In the summer, it is fine.

[skip1930]

"...I have to keep it partially choked to keep it from stalling out at low speeds..."

I'd guess that the fuel is not vaporizing. Liquids do not burn. As suggested, 'MORE HEAT'.
I don't know but I have never run across a thermstat on a 2 cycle outboard engine.

skip.

[Salty19]

I use sea foam to prevent clogged carb jets, but if problems begin...the only real way to fix is to remove carb, disassemble and use carb cleaner with compressed air to clean the jets and orifices. Works extremely well.

Being a sailor forces one to learn how to do this occasionally. Being an old dirt biker, one learns fast how to clean dirty carbs.  Your carb is very simple to remove and clean...I suggest doing so!

[Glenn Basore]

Salty,

I have few concerns about rebuilding the carb,

1. This is a Calif. OB with all the emission tags on it.
2. I don't know if I can buy parts ( gaskets etc) to rebuild it based upon # 1
3. I haven't had the best success with rebuilding carbs, at least on cars.

Note,

I had to special order the fuel pump and had a hard time locating it.

Glenn

[MacGyver]

Yes they do sometimes have tstats on them.
They are also getting fuel injection on the smaller ones now, I think it is honda that is at a 9.9 now last I heard

Stabil is made from the same compnents that used to comprise the chemicals used to "soak" a carb years ago.
That is why I suggest it.

One thing I have noticed is that the smaller motors have issues when it is colder.

The question was how to fix Glenns issue, I would try the Stabil in slightly higher than reccomended but not too higher than what they say as you are using small amounts of fuel anyway.
Use fresh gasoline of high grade (we sell 93 on the dock)
Run that engine for a good amount of time. Like an hour? That will give it enough time to get the line cleared if you didnt do it before running it
And will give it time to get the chems into that carb.
This isnt a overnight clearing.....it will take.some time to get it cleared out.

Glenn, I will make a video showing how to use the engines pressure to help clear that carb out.
I will post that link here. Using that pressure will help pull the junk through ( we are talking micron junk or issue) and once it hits that combustion chamber it will be gone like the wind (hopefully)

If this sounds angry, i am sorry.....just got off phone with insurance company........

Mac

[Salty19]

Glenn, you can definitely get parts and gaskets! I promise you cleaning these carbs are EASY.

[MacGyver]

 
Found this that my friend said I emailed to him a while back on his motor.

"Hey dude, my uncle taught me a trick, worked on the moped, and worked at work on the Honda 8hp.

After a few runs with the Stabil in it, to allow it to work, and dont forget the fresh high grade fuel you cheap bastard, that will help break things up somewhat or atleast loosen it up.
Run the engine out of gear, perhaps even get it warm but that isnt what he did on the moped. Rev it up to get it up to about 3/4 throttle, then with your hand cover the air intake. Then drop the throttle. The engine should go like it is going to die, as you starved it for air for a brief amount of time.
This action will actually cause the pressure in the system to pull that crap through like sucking soda through a straw.
That moped is tight, to get the 120 MPG out of it, compared to your measily 60 mpg. And that is what the issue was, crap in the system.

You want to pull your hand off somewhat fast, as it is just to get it to demand air bigtime through the carb mixture then your hand stops the air almost completely (face it you probably dont totally close off air access with you big pudgy hands anyway) sucking the trash through.

Worst case scenario, you have to rebuild the carb, but you are there any way right?
That Honda, it worked after doing it numerous times, letting it run high for a little then doing that hand maneuver it till she almost died, then back into the throttle to help the engine recover. I did not remove the air cleaner to do that. so it was getting some air in other spots I am sure....
Just when I was about to give up, she got through it. That honda never really held idle too well, but it is noticeably better now.

Anyway, let me know what happens.
Jason"

Minus the heckling, there is good info there.
Hope that helps maybe, it has worked several more times for me, and one time did not, but that carb had big time things wrong anyway, as I found out when I disassembled it.

That info coming from my uncle is like gold, he has been a mechanic (and a damn good one to boot) for around 35 to 40 years. maybe a little longer as he started when he was really young with dirt bikes and such.

Mac

[Koinonia]

time to buy my old 10hp diesel and do an inboard conversion!